Known dry-cleaning processes consist of a wash, rinse, and drying cycle with solvent recovery. Garments are loaded into a basket in a cleaning drum and immersed in a dry-cleaning fluid or solvent, which is pumped into the cleaning drum from a base tank. Conventional dry-cleaning fluids include perchloroethylene (PCE), petroleum-based or Stoddard solvents, CFC-113, and 1,1,1-trichloroethane, all of which are generally aided by a detergent. The solvent is used to dissolve soluble contaminants, such as oils, and to entrain and wash away insoluble contaminants, such as dirt.
The use of these conventional solvents, however, poses a number of health and safety risks as well as being environmentally hazardous. For example, halogenated solvents are known to be environmentally unfriendly, and at least one of these solvents, PCE, is a suspected carcinogen. Known petroleum-based solvents are flammable and can contribute to the production of smog. Accordingly, dry cleaning systems which utilize dense phase fluids, such as liquid carbon dioxide, as a cleaning medium have been developed. An apparatus and method for employing liquid carbon dioxide as the dry-cleaning solvent is disclosed in U.S. Pat. No. 5,467,492, entitled "Dry-Cleaning Garments Using Liquid Carbon Dioxide Under Agitation As Cleaning Medium". A similar dry cleaning apparatus is also disclosed in U.S. Pat. No. 5,651,276.
These systems pose a number of other problems, particularly in relation to the high operating pressures necessary for maintaining the gas in a liquid state. For example, the various pressurized components of the system must be constructed with thick, heavy walled structures to withstand the elevated pressures encountered during the dry cleaning operation. These bulky structures can consume a significant amount of space. In order to encourage dry cleaning operators to convert to liquid carbon dioxide dry cleaning systems, these new systems must be configured so as to minimize space consumption. This is necessary to enable such systems to be placed into facilities and locations designed for existing dry-cleaning equipment. Moreover, due to the neighborhood nature of many dry cleaning operations, there can be even greater space limitations. Thus, while minimizing space requirements is always an important object, it is particularly important with dry cleaning equipment.
In terms of space consumption, one of the more critical aspects of a liquifiable gas dry-cleaning apparatus is the area required for opening and closing of the access door of the pressurized cleaning vessel to permit loading and removal of garments or other items for cleaning. Since the cleaning vessel in a liquid carbon dioxide system operates at a high pressure (e.g. 700-850 psi) under ambient temperature conditions in order to ensure that the carbon dioxide remains in a liquid phase, a relatively bulky, heavy walled door must be used. One type of door which could be used on such a liquid carbon dioxide cleaning vessel is a conventional hinged door. Due to the weight of the door, an opening mechanism typically would have to be provided for swinging the door to an open position at the side of the cleaning vessel. However, with such a hinged door a significant amount of clearance would have to be provided both in front of the cleaning vessel, to allow for the swinging motion of the door, and to at least one side of the cleaning vessel. Moreover, additional space would have to be provided for the door opening and closing mechanism.
While the need to minimize space consumption in the front of the cleaning vessel might be satisfied by using a door which could slide horizontally into an open position, clearance again would have to be provided on at least one side of the cleaning vessel to allow for the open door. Additionally, the mechanism for horizontally sliding the door to the open position would have to be arranged to the side of the cleaning vessel and likely would require additional space.
Not only does the bulk and size of the removable door and its opening mechanism consume floor space, they further may impede access to the cleaning chamber when the door is opened. Moreover, if any part of the door or its opening mechanism is moved to a position in front of the cleaning vessel as a result of the door opening operation, it can extend the axial reach necessary for an operator to manually reach into the cleaning chamber to load or unload items therein.
Hence, the need exists in the art for a door opening and closing mechanism for such pressurized cleaning vessels that can be operated with minimal space requirements. Due to the bulk and weight of the door, and the necessity for manipulating the door within relatively small space constraints, it further has been difficult to quickly and reliably move and lock the door in precise aligned relation with the pressure vessel. Moreover, heretofore if the door opening and closing mechanism did not move the door with straight axial movement into and out of engagement with the pressure vessel, difficulties could result in properly engaging locking elements necessary for securing the door. High stress concentrations also can occur to the locking elements during usage which can cause metal fatigue and failure.